If you didn't download the Strawberry Demo and want the FM10 'dark' skin you can download it from here.
To use the skin, you will need to copy BOTH folders from within the .zip ('fm10 dark' and 'fm10 dark-widgets') here:
Win Vista: C:\Users\<username>\Documents\Sports Interactive\Football Manager 2010 demo\skins\
Win 2000/XP: C:\Documents and Settings\<username>\My Documents\Sports Interactive\Football Manager 2010 demo\skins\
Win 98/ME: C:\My Documents\Sports Interactive\Football Manager 2010 demo\skins\
Mac OS X: /Users/<username>/Documents/Sports Interactive/Football Manager 2010 demo/skins/
The 'skins' folder may already be there or it may need to be created - do that if you need to. Simply drag your extracted folders ('fm10 dark' and 'fm10 dark-widgets') into the skins folder.
These will not work with the FM10 skin as they have been disabled. Other skins should be able to re-enable them if skinners choose to.
These have changed slightly from FM 09. The colours are now held in the "skins/<SKIN_NAME>/settings/<SKIN_NAME> settings.xml" file.